Halogen-free low dielectric resin composition, and pre-preg, metal-clad laminate, and printed circuit board using the same

ABSTRACT

A halogen-free low dielectric resin composition is provided. The halogen-free low dielectric resin composition includes:
     (A) a polyphenylene ether which has an unsaturated functional group;   (B) a cross-linking agent which has an unsaturated functional group; and   (C) a phosphorus-containing compound represented by the following formula (I),

CLAIM FOR PRIORITY

This application claims the benefit of Taiwan Patent Application No.107130020 filed on Aug. 28, 2018, the subject matters of which areincorporated herein in their entirety by reference.

BACKGROUND Field of the Invention

The present invention provides a halogen-free low dielectric resincomposition, especially a polyphenylene ether resin composition ofhalogen-free electronic materials having the following advantages: a lowdielectric constant (Dk), a low dissipation factor (Df), a lowcoefficient of thermal expansion and high dimensional stability. Thehalogen-free low dielectric resin composition of the present inventioncan be used in combination with glass fibers to constitute a compositematerial or prepreg. Furthermore, it can be used as a metal foiladhesive to manufacture a resin-coated copper (RCC), a metal-cladlaminate, a printed circuit board (PCB) and so on.

Descriptions of the Related Art

Recently, in the field of electronic telecommunications, electronicproducts have been designed to operate at higher frequencies and speedsdue to the increasing amount of data transmission; therefore, thedielectric properties of the related electronic materials need to beenhanced. In consideration of the trends of high-frequency andhigh-speed signal transmission, the miniaturization of electronicelements, and high-density wiring of PCBs, there is a big need forelectronic materials with low dielectric properties, but conventionalelectronic materials are increasingly failing to meet this need.

Furthermore, due to growing environmental awareness, halogen-containingflame retardants are gradually being replaced by halogen-free flameretardants, such as metal hydroxides, nitrogen-containing compounds,phosphorus-containing compounds, etc. However, when using conventionalhalogen-free flame retardants in a resin composition, the dielectricproperties of the prepared electronic materials usually degrade. Forexample, the prepared electronic materials usually have higher Dk valuesor Df values. If the formation of the resin composition is adjusted tomaintain good dielectric properties of the electronic materials, thephysical properties of the electronic materials may often degrade. Forexample, the peeling strength, dimensional stability or heat resistancemay degrade. Therefore, there is a need for a high-frequency,halogen-free electronic material with low Dk and Df values, while havingsatisfactory physical properties.

SUMMARY

The problem to be solved by the present invention is that conventionalhalogen-free electronic materials do not simultaneously exhibitsatisfactory high-frequency dielectric properties, heat resistance anddimensional stability, which makes it difficult for the preparedmetal-clad laminates or printed circuit boards to meet the requirementsespecially with regard to the high temperature aging test. To this end,the present invention provides a halogen-free low dielectric resincomposition whereby an electronic material prepared therefrom can havegood high-frequency dielectric properties (for example, a measured Dkvalue less than 4.0 and a measured Df value less than 0.006 at 10 GHz)and good high-temperature resistance, such that the electronic materialcan meet the requirements especially with regard to the high temperatureaging test.

As described in the following objectives of the present invention, thetechnical means applied in the present invention for solving theproblems of the prior art is to use a phosphorus-containing compoundhaving a specific structure in the polyphenylene ether resincomposition. The halogen-free electronic material prepared from thehalogen-free low dielectric resin composition of the present invention(herein also called the resin composition of the present invention)possesses not only high-temperature resistance and dimensionalstability, but also lower Dk and Df values. Therefore, the electronicmaterial prepared from the resin composition of the present invention isparticularly suitable for high-frequency applications and can meet thehigh requirements of materials for advanced telecommunicationapplications. Examples of the high-frequency applications include butare not limited to 5th generation mobile networks (usually called 5Gnetworks), advanced driver assistance systems (ADAS), and artificialintelligence (AI) applications.

An objective of the present invention is to provide a halogen-free lowdielectric resin composition, which comprises the following components:

(A) a polyphenylene ether resin having an unsaturated functional group;

(B) a cross-linking agent having an unsaturated functional group; and

(C) a phosphorus-containing compound represented by the followingformula (I):

In some embodiments addressing this foregoing objective of the presentinvention, the halogen-free low dielectric resin composition furthercomprises a reactive phosphorus compound having an unsaturatedfunctional group

In some embodiments of the present invention, the weight ratio of thephosphorus-containing compound (C) represented by formula (I) to thereactive phosphorus compound is from 4:1 to 1:4.

In some embodiments of the present invention, the reative phosphoruscompound is an ally cyclophosphazene compound.

In some embodiments of the present invention, the polyphenylene etherresin (A) is represented by the following formula (II):

wherein,

R₃₁, R₃₂, R₃₃ and R₃₄ are independently H, or a substituted orunsubstituted C1-C5 alkyl;

A₁ and A₂ are independently

X and Y are independently absent, or carbonyl or an alkenyl-containinggroup;

m and n are independently an integer from 0 to 100, with the provisothat m and n are not 0 at the same time; and

Z is absent, or aryl, —O—,

wherein R₃₅ and R₃₆ are independently H or a C1-C12 alkyl.

In some embodiments of the present invention, the cross-linking agent(B) is selected from the group consisting of a polyfunctional allyliccompound, a polyfunctional acrylate, a polyfunctional acrylamide, apolyfunctional styrenic compound, a bismaleimide compound, andcombinations thereof.

In some embodiments of the present invention, the cross-linking agent(B) is selected from the group consisting of triallyl isocyanurate(TAIC), triallyl cyanurate (TAC), prepolymers thereof, and combinationsthereof.

In some embodiments of the present invention, the halogen-free lowdielectric resin composition further comprises a phosphorus-containingadditive flame retardant selected from the group consisting of aphosphinate salt, a polyphosphate salt, a phosphonium salt, a phosphateester, a phosphazene, a phosphite ester, a phosphine oxide, andcombinations thereof.

In some embodiments of the present invention, the halogen-free lowdielectric resin composition further comprises a vinyl-containingelastomer selected from the group consisting of polybutadiene,styrene-butadiene (SB) copolymer, styrene-butadiene-styrene (SBS)di/tri-block copolymer, polyisoprene, styrene-isoprene copolymer,styrene-i soprene-styrene (SIS) block copolymer, acrylonitrile-butadienecopolymer, acrylonitrile-butadiene-styrene block copolymer, andcombinations thereof. When the halogen-free low dielectric resincomposition includes a vinyl-containing elastomer, the cross-linkingagent (B) is preferably a bismaleimide compound.

In some embodiments of the present invention, the halogen-free lowdielectric resin composition further comprises a filler selected fromthe group consisting of silica (for example, spherical silica, fusedsilica, non-fused silica, porous silica, or hollow silica), aluminumoxide, aluminum hydroxide, magnesium oxide, magnesium hydroxide, calciumcarbonate, talc, clay, aluminum nitride, boron nitride, silicon nitride,silicon aluminum carbide, silicon carbide, sodium carbonate, magnesiumcarbonate, titanium dioxide, zinc oxide, zirconium oxide, quartz,diamond powder, diamond-like powder, graphite, graphene, potassiumtitanate, strontium titanate, barium titanate, ceramic fiber, zincmolybdate, ammonium molybdate, zinc borate, calcium phosphate, calcinedkaolin, pryan, mica, boehmite, hydrotalcite, carbon nanotube,polytetrafluoroethylene (PTFE) powder, hollow glass bead, nanosizedinorganic powder, and combinations thereof.

In some embodiments of the present invention, based on the total weightof the resin solid content, the amount of the phosphorus-containingcompound (C) represented by formula (I) is 1 wt % to 50 wt %.

In some embodiments of the present invention, the weight ratio of thepolyphenylene ether resin (A) to the cross-linking agent (B) is from 3:1to 1:1.

Another objective of the present invention is to provide a prepreg,which is prepared by impregnating a substrate with the abovementionedresin composition or by coating the abovementioned resin compositiononto a substrate, and drying the impregnated or coated substrate.

Yet another objective of the present invention is to provide ametal-clad laminate, which is prepared by laminating the abovementionedprepreg and a metal foil, or by directly coating the abovementionedresin composition onto a metal foil and drying the coated metal foil.

Yet another objective of the present invention is to provide a printedcircuit board, which is prepared from the abovementioned metal-cladlaminate.

To render the above objectives, technical features and advantages of thepresent invention more apparent, the present invention will be describedin detail with reference to some embodiments hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Not applicable.

DETAILED DESCRIPTION

Hereinafter, some embodiments of the present invention will be describedin detail. However, without departing from the spirit of the presentinvention, the present invention may be embodied in various embodimentsand should not be limited to the embodiments described in thespecification.

Unless it is additionally explained, the expressions “a,” “the,” or thelike recited in the specification (especially in the claims) shouldinclude both the singular and the plural forms.

Unless it is additionally explained, while describing constituents in asolution, mixture or composition in the specification, the amount ofeach constituent is calculated based on the dry weight, i.e., regardlessof the weight of the solvent.

As used herein, the term “resin solid content” refers to all the othersolid components excluding fillers in the resin composition. That is,the resin solid content includes a polyphenylene ether resin, across-linking agent, a phosphorus-containing compound represented byformula (I) as necessary components, and optional components (forexample, a reative phosphorus compound, a phosphorus-containing additiveflame retardant, and a vinyl-containing elastomer).

As used herein, the term “halogen-free” refers to a resin compositionsubstantially free of halogen, especially chlorine (Cl) and bromine (Br)to comply with the halogen-free standard for electronic products definedby the International Electrotechnical Commission (IEC). IEC-61249-2-21defines “halogen-free” for electronic products as follows: Br<900 ppm,Cl<900 ppm, and (Cl+Br)<1500 ppm.

Compared with the prior art, the distinguishing feature of the presentinvention lies in that the halogen-free low dielectric resin compositionof the present invention includes a phosphorus-containing compound witha specific structure, which can impart good high-temperature resistanceto the prepared electronic material. In addition, compared with otherresin compositions having a phosphorus-containing compound withouthaving the structure of formula (I), the resin composition of thepresent invention can improve the dielectric properties of electronicmaterials without sacrificing the physicochemical properties and heatresistance properties of the prepared electronic materials, to thussolve the problems of conventional resin compositions. Detaileddescriptions for each component of the halogen-free low dielectric resincomposition and the preparation method of the resin composition areprovided as follows.

1. RESIN COMPOSITION

The resin composition of the present invention comprises a polyphenyleneether resin having an unsaturated functional group (A), a cross-linkingagent (B) having an unsaturated functional group and aphosphorus-containing compound (C) represented by formula (I) asnecessary components, and other optional components that may be useddepending on the need. Detailed description for each component of theresin composition are provided as follows.

1.1. Polyphenylene Ether Resin (A)

As used herein, a polyphenylene ether resin refers to a resin having atleast a repeating unit

in the main chain and having an unsaturated functional group at theterminal, wherein Rs are independently H or a C1-C5 alkyl, and v is aninteger ranging from 1 to 100. The unsaturated functional group refersto a group capable of carrying out addition polymerization with othercomponents having an unsaturated functional group, and the additionpolymerization reaction can be initiated by light or heat in thepresence of a polymerization initiator. Examples of the unsaturatedfunctional group include but are not limited to vinyl, vinyl benzyl,allyl, acryloyl, acrylate, and methacrylate. Examples of thepolyphenylene ether resin having an unsaturated functional group includebut are not limited to a vinyl-containing polyphenylene ether resin, anallyl-containing polyphenylene ether resin, a vinyl benzyl-containingpolyphenylene ether resin, an acryloyl-containing polyphenylene etherresin, an acrylate-containing polyphenylene ether resin and amethacrylate-containing polyphenylene ether resin. Each of thepolyphenylene ether resin having an unsaturated functional group caneither be used alone or in any combination.

The method for preparing the polyphenylene ether resin having anunsaturated functional group is not the technical feature of the presentinvention, and persons having ordinary skill in the art can conduct themethod based on the disclosure of the present invention and ordinaryskill. The related methods for preparing the polyphenylene ether resinhaving an unsaturated functional group are described in, for example,U.S, patent application Ser. No. 6,995,195 B2 for vinyl-containingpolyphenylene ether resins, U.S. patent application Ser. No. 5,218,030 Afor vinyl-containing polyphenylene ether resins, U.S. patent applicationSer. No. 5,352,754 A for allyl-containing polyphenylene ether resins,U.S. patent application Ser. No. 6,352,782 B2 formethacrylate-containing polyphenylene ether resins, and US 2016/0280913A1, all of which are incorporated herein in their entireties byreference.

Examples of commercially available polyphenylene ether resin (A) havingan unsaturated functional group include CPE-2ST and OPE-2EA availablefrom MITSUBISHI GAS CHEMICAL company, SA-9000 available from SABICcompany, PP807 available from Chin Yee Chemical Industry company, and apolyphenylene ether resin available from ASAHI KASEI company.

In some embodiments of the present invention, the polyphenylene etherresin (A) having an unsaturated functional group is represented by thefollowing formula (II).

In formula (II), R₃₁, R₃₂, R₃₃ and R₃₄ are independently H, or asubstituted or unsubstituted C1-C5 alkyl, and preferably —CH₃; A₁ and A₂are independently

and preferably

X and Y are independently absent, or carbonyl or an alkenyl-containinggroup, and preferably absent; m and n are independently an integer from0 to 100, with the proviso that m and n are not 0 at the same time; andZ is absent, or aryl, —O—,

wherein R₃₅ and R₃₆ are independently H or a C1-C12 alkyl, and Z ispreferably

In the resin composition of the present invention, the polyphenyleneether resin (A) having an unsaturated functional group may have a weightaverage molecular weight (Mw) from 1000 to 50,000, preferably from 1000to 10,000, and more preferably from 1000 to 5000. If the Mw of thepolyphenylene ether resin is greater than the abovementioned range, theproperties of the resin composition, such as fluidity, solubility, etc.,may degrade, which makes it difficult for subsequent processing. On theother hand, if the Mw of the polyphenylene ether resin is less than theabovementioned range, the electrical properties and thermal stability ofthe resin composition may degrade.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of the polyphenylene etherresin (A) having an unsaturated functional group can range from 30 wt %to 65 wt %, and more specifically from 35 wt % to 60 wt %, such as 36 wt%, 37 wt %, 38 wt %, 39 wt %, 40 wt %, 41 wt %, 42 wt %, 43 wt %, 45 wt%, 47 wt %, 48 wt %, 50 wt %, 52 wt %, 53 wt %, 55 wt %, 56 wt %, 58 wt%, or 59 wt %.

1.2. Cross-Linking Agent (B)

As used herein, a cross-linking agent refers to a component having anunsaturated functional group and being capable of undergoingcrosslinking reaction with a polyphenylene ether resin to form a stereonetwork structure, wherein the unsaturated functional group is asdefined above. In the resin composition of the present invention, thecross-linking agent preferably has good compatibility with thepolyphenylene ether resin, such that the formed resin composition canhave a good appearance after curing. In general, the cross-linking agenthaving an unsaturated functional group may be classified into amonofunctional cross-linking agent and a polyfunctional cross-linkingagent depending on the amount of the unsaturated functional group,wherein the monofunctional cross-linking agent has only an unsaturatedfunctional group, and the polyfunctional cross-linking agent has atleast two unsaturated functional groups. In some embodiments of thepresent invention, in order that the resin composition has a highercrosslinking density after curing, it is preferred to use apolyfunctional cross-linking agent.

Examples of the polyfunctional cross-linking agent include but are notlimited to a polyfunctional allyl-based compound, a polyfunctionalacrylate, a polyfunctional styrene-based compound, a bismaleimidecompound, and a polyfunctional acrylamide. Each mentioned polyfunctionalcross-linking agent can either be used alone or in any combination.

As used herein, a polyfunctional allyl-based compound refers to acompound containing at least two allyl groups. Examples of thepolyfunctional allyl-based compound include but are not limited todiallyl phthalate, diallyl isophthalate, triallyl trimellitate, triallylmesate, triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), andprepolymers thereof.

As used herein, a polyfunctional acrylate refers to a compoundcontaining at least two acrylate groups. Examples of the polyfunctionalacrylate include but are not limited to trimethylolpropanetri(meth)acrylate, 1,6-hexanediol di(meth)acrylate, ethylene glycoldi(meth)acrylate, propylene glycol di(meth)acrylate, 1,3-butanedioldi(meth)acrylate, 1,4-butanediol di(meth)acrylate, cyclohexanedimethanol di(meth)acrylate, diethylene glycol di(meth)acrylate,triethylene glycol di(meth)acryl ate, and prepolymers thereof.

As used herein, a polyfunctional styrene-based compound refers to acompound having at least two alkenyl groups attached to the aromaticring. Examples of the polyfunctional styrene-based compound include butare not limited to 1,3-divinylbenzene, 1,4-divinylbenzene,trivinylbenzene, 1,3 -diisopropenylbenzene, 1,4-diisopropenylbenzene,1,2-bis(p-vinylphenyl)ethane, 1,2-bis(m-vinylphenyl)ethane,1-(p-vinylphenyl)-2-(m-vinylphenyl)-ethane,1,4-bis(p-vinylphenylethyl)benzene, 1,4-bis(m-vinylphenyl ethyl)benzene,1,3-bis(p-vinylphenylethyl)benzene, 1,3 -bis(m-vinylphenylethyl)benzene, 1-(p-vinylphenylethyl)-4-(m-vinylphenylethyl) benzene,1-(p-vinylphenylethyl)-3 -(m-vinylphenylethyl)benzene, and prepolymersthereof.

As used herein, a bismaleimide compound refers to a compound having atleast two of maleimide functional groups. A maleimide functional grouphas reactive double bonds and thus can react with other componentshaving unsaturated functional groups. In some embodiments of the presentinvention, the bismaleimide compound is represented by the followingformula (III):

In formula (III), R₁ is an organic group and preferably selected fromthe following group consisting of: methylene (—CH₂—),4,4′-diphenylmethane

m-phenylene

bisphenol A diphenyl ether

3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethane group

4-methyl-1,3-phenylene

and 2,2,4-trimethyl-1,6-hexylene

Specific examples of the bismaleimide compound include but are notlimited to 1,2-bismaleimidoethane, 1,6-bismaleimidohexane,1,3-bismaleimidobenzene, 1,4-bismaleimidobenzene,2,4-bismaleimidotoluene, 4,4′-bismaleimidodiphenylmethane,4,4′-bismaleimidodiphenyl ether, 3,3′-bismaleimidodiphenyl sulfone,4,4′-bismaleimidodiphenyl sulfone, 4,4′-bismaleimidodicyclohexylmethane,3,5-bis(4-maleimidophenyl)pyridine, 2,6-bismaleimidopyridine, 1,3-bis(maleimidomethyl)cylcohexane, 1,3 -bis(maleimidomethyl)benzene,1,1-bis(4-maleimidophenyl)cyclohexane, 1,3-bis(dichloromaleimido)benzene, 4,4′-biscitraconimidodiphenylmethane,2,2-bis(4-maleimidophenyl)propane,1-phenyl-1,1-bis(4-maleimidophenyl)ethane, α,α-bis(4-maleimidophenyl)toluene, 3,5-bismaleimido-1,2,4-triazole,N,N′-ethylenebismaleimide, N,N′-hexamethylenebismaleimide,N,N′-m-phenylenebismaleimide, N,N′-p-phenylenebismaleimide,N,N′-(4,4′-diphenylmethane)bismaleimide, N,N′-(4,4′-diphenyl ether)bismaleimide, N,N′-(4,4′-diphenylsulfone) bismaleimide,N,N′-(4,4′-dicyclohexylmethane) bismaleimide, N,N′-α,α′-4,4′-dimethylenecyclohexane bismaleimide, N,N′-m-dimethylphenylbismaleimide,N,N′-(4,4′-diphenylcyclohexane)bismaleimide and N,N′-methylenebis(3-chloro-p-phenylene)bismaleimide. Commercially availablebismaleimide resins include BMI-70 and BMI-80 available from KI Chemicalcompany and BMI-1000, BMI-4000, BMI-5000, BMI-5100, BMI-7000, BMI-2000and BMI-2300 (CAS 67784-74-1) available from Daiwa Fine Chemicalcompany. The aforementioned bismaleimide can either be used alone or inany combination, and persons with ordinary skill in the art could adjustthe amount of the bismaleimide depending on the need. In the appendedexamples, 3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethylbismaleimide(that is, in formlua (III), R₁ is3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethyl group

is used.

Considering the compatibility between the components of the resincomposition, the cross-linking agent (B) is preferably selected from thefollowing group consisting of: TAIC, TAC, 1,3-divinylbenzene,1,4-divinylbenzene, 1,2-bis(p-vinylphenyl)ethane,1,2-bis(m-vinylphenyl)ethane,1-(p-vinylphenyl)-2-(m-vinylphenyl)-ethane,3,3′-dimethyl-5,5′-diethyl-4,4′-diphenylmethylbismaleimide, andcombinations thereof.

In the resin composition of the present invention, the cross-linkingagent (B) having an unsaturated functional group may have a Mw from 100to 50,000, preferably from 100 to 4000, and more preferably from 100 to3000. If the Mw of the cross-linking agent is greater than theabovementioned range, the viscosity (such as dynamic viscosity) of theresin composition may be too high, which is disadvantageous forsubsequent processing. If the Mw of the cross-linking agent is less thanthe abovementioned range, the cross-linking agent is easily volatilizedduring the curing of the resin composition, and the components in theresin composition may not maintain the desired ratio after curing.

In the resin composition of the present invention, the weight ratio ofthe polyphenylene ether resin (A) having an unsaturated functional groupto the cross-linking agent (B) having an unsaturated functional groupmay be from 95:5 to 5:95, preferably from 90:10 to 30:70, morepreferably 90:10 to 50:50, and particularly preferably 90:10 to 60:40.If the weight ratio of the polyphenylene ether resin is too low (thatis, the weight ratio of the cross-linking agent is too high), forexample, less than the abovementioned range, the prepared electronicmaterial may not have good dielectric properties. If the weight ratio ofthe polyphenylene ether resin is too high (that is, the weight ratio ofthe cross-linking agent is too low), for example, higher than theabovementioned range, the crosslinking density of the resin compositionafter curing may be insufficient, thereby adversly affecting the heatresistance and dimensional stability of the prepared electronicmaterials.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of the cross-linking agent(B) having an unsaturated functional group can range from 10 wt % to 35wt %, and more specifically from 12 wt % to 33 wt %, such as 13 wt %, 14wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 23wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, 30 wt %, or32 wt %.

1.2. Phosphorus-Containing Compound (C) Represented by Formula (I)

The resin composition of the present invention comprises aphosphorus-containing compound (C) represented by the following formula(I):

The phosphorus-containing compound represented by formula (I) is aderivative of a phosphazene compound, specificallytri-(2,2′-dihydroxybiphenyl) cyclophosphazene (CAS 6800-71-1). In theresin composition, the phosphorus-containing compound represented byformula (I) is an additive component and does not undergo chemicalreactions with other components in the resin composition.

In general, a phosphorus-containing compound often used in the resincomposition usually has a love melting point. for instance commerciallyavailable hexaphenoxy cyclotriphosphazene (e.g. SPB-100 available fromOtsuka Chemical company) only has a melting point from 100° C. to 120°C. In contrast, the phosphorus-containing compound represented byformula (I) used in the resin composition of the present invention has amelting point higher than 260° C. Without being bound by theory, it isbelieved that this high melting point results from thephosphorus-containing compound of formula (1) having a very rigidbiphenyl structure and a plurality of cyclic structures. It has beenfound that, by including the phosphorus-containing compound of formula(I) and the polyphenylene ether resin (A) having an unsaturatedfunctional group in the resin composition of the present invention, theelectronic material prepared therefrom can have not only excellenthigh-temperature resistance but also low coefficient of thermalexpansion to have excellent dimensional stability.

The phosphorus-containing compound represented by formula (I) can beprepared by reacting hexachloro cyclophosphazene

with 2,2′-dihydroxy biphenyl

at an appropriate ratio followed by further purification. Detaileddescription for the preparation method of the phosphorus-containingcompound represented by formula (I) can be also found in, for example,US 2011/0130497 and TW 445276, all of which are incorporated herein intheir entireties by reference. Commercially availablephosphorus-containing compound represented by formula (I) include BP-PZavailable from Otsuka Chemical company.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of thephosphorus-containing compound (C) represented by formula (I) can rangefrom 1 wt % to 50 wt %, and more specifically from 1.5 wt % to 45 wt %,such as 2 wt %, 2.5 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt%, 9 wt %, 10 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt%, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 22 wt %, 24 wt %, 25 wt %, 26 wt%, 28 wt %, 30 wt %, 32 wt %, 33 wt %, 35 wt %, 36 wt %, 38 wt %, 40 wt%, 41 wt %, 42 wt %, or 43 wt %. In addition, the amount of thephosphorus-containing compound represented by formula (I) is preferablyused in an amount so that the total amount of the phosphorus atoms inthe resin composition is at least 1 wt %, and more preferably from 1 wt% to 6 wt %, based on the total weight of the resin solid content, toallow the prepared electronic material to have good flame retardance, aswell as good moisture resistance, dielectric properties and peelingstrength, all at the same time.

1.4. Other Optional Components (D)

The resin composition of the present invention may optionally furthercomprise other optional compoents, such as elastomers,phosphorus-containing additive flame retardants, phosphorus-containingreactive flame retardants, fillers, epoxy resins and additiveswell-known to persons having ordinary skill in the art, as illustratedbelow, to adaptively improve the workability of the resin compositionduring manufacturing or the physicochemical properties of the electronicmaterial prepared from the resin composition. The additives well-knownto persons having ordinary skill in the art include but are not limitedto curing agents, curing accelerators and dispersing agents.

1.4.1. Vinyl-Containing Elastomer

As used herein, an elastomer refers to a polymer having viscoelasticitywhich imparts toughness to an electronic material. In some embodimentsof the present invention, the resin composition further includes avinyl-containing, elastomer which can undergo a crosslinking reactionwith other components having an unsaturated functional group, such thatthe prepared electronic material has better toughness and lower Dk andDf values.

In general, a vinyl-containing, elastomer is formed by polymerization ofmonomers having carbon-carbon unsaturated bonds, and a pendant vinylgroup is present on the main chain of the polymer or a branch or aterminal group thereof, wherein the pendant vinyl content usuallyexpressed as a percentage is preferably greater than 10%, and morepreferably greater than 50%.

The vinyl-containing elastomer may be, for example, a homopolymerpolymerized from conjugated-diene monomers, and a copolymercopolymerized from a conjugated-diene monomers and other monomers. TheMw of the vinyl-containing elastomer may be from 200 to 100,000,preferably from 1000 to 5000, and more preferably from 1000 to 3000.Examples of the conjugated-diene monomers include butadiene andisoprene, and examples of other monomers include styrene and maleicanhydride.

The vinyl-containing elastomer may be selected from but are not limitedto polybutadiene, styrene-butadiene copolymer, styrene-butadiene-styrene(SBS) di/tri block copolymer, polyisoprene, styrene-isoprene copolymer,styrene-isoprene-styrene (SIS) di/tri block copolymer,acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene blockcopolymer, and combinations thereof.

Commercially available vinyl-containing elastomers include Ricon 150,Ricon 100, Ricon 181, Ricon 184, Ricon 104H, Ricon 250, Ricon 257, Ricon157, Ricon 130, Ricon 130MA and Ricon 184MA available from Cray Valleycompany, B3000 available from Nippon Soda company, and Kraton DX1300available from Shell Oil company.

In some embodiments of the present invention, when the resin compositionincludes a vinyl-containing elastomer, the cross-linking agent (B) ispreferably a bismaleimide compound. The vinyl-containing elastomer andthe bismaleimide compound can exhibit good synergisticcomplementariness, such that the prepared electronic material providesboth good dielectric properties and heat resistance.

In the resin composition of the present invention, the weight ratio ofthe polvphenylene ether resin (A) having an unsaturated functional groupto the vinyl-containing elastomer is preferably from 90:10 to 50:50, andmore preferably from 70:30 to 60:40. If the weight ratio of thevinyl-containing elastomer is too high (for example, higher than theabovementioned range), the heat resistance and the dimensional stabilityof the prepared electronic material may decrease. If the weight ratio ofthe vinyl-containing elastomer is too low (for example, less than theabovementioned range), the vinyl-containing elastomer is insufficient toprovide the desired toughening effect, which may result in thedeterioration of the physical properties of the prepared electronicmaterial.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of the vinyl-containingelastomer can range from 0 wt % to 35 wt %, and more particularly from10 wt % to 30 wt %, such as 12 wt %, 15 wt %, 18 wt %, 20 wt %, 21 wt %,22 wt %, 23 wt %, 25 wt %, 27 wt %, or 28 wt %.

1.4.2. Phosphorus-Containing Additive Flame Retardant

The resin composition of the present invention may optionally furthercomprise phosphorus-containing additive flame retardants to improve theheat resistance and the dimensional stability. As used herein, aphosphorus-containing additive flame retardant refers to aphosphorus-containing compound without reactive unsaturated functionalgroups and without the structure of formula (I). In order to meet thehalogen-free requirements of the resin composition of the presentinvention, the phosphorus-containing additive flame retardant ispreferably free of halogen. Examples of the phosphorus-containingadditive flame retardant include but are not limited to phosphinate,polyphosphate, phosphonium salt, phosphate ester, phosphazene, phosphiteester, and phosphine oxide.

Examples of the phosphinate include but are not limited to aluminumdialkylphosphinate, aluminum tris(diethylphosphinate), aluminumtris(methylethylphosphinate), aluminum tris(diphenylphosphinate), zincbis(diethylphosphinate), zinc bis(methylethylphosphinate), zincbis(diphenylphosphinate), titanyl bis(diethylphosphinate), titanylbis(methylethylphosphinate), and titanyl bis(diphenylphosphinate). Onecommercially available phosphinate is OP935 available from CLARIANTcompany.

Examples of the polyphosphate include but are not limited to melaminepolyphosphate, melam polyphosphate, and melem polyphosphate. Onecommercially available polyphosphate is Melapur 200, available from BASFcompany.

An example of the phosphonium salt is, but is not limited totetraphenylphosphonium tetraphenylborate. Examples of the phosphateester include but are not limited to a condensed phosphate estercompound, and a cyclic phosphate ester compound. Examples of thecondensed phosphate ester compound include but are not limited totriphenyl phosphate, tricresyl phosphate, xylenyl-diphenyl phosphate,cresyl-diphenyl phosphate, resorcinol bis-xylenylphosphate (RXP),resorcinol bis-diphenylphosphate (RDP), and9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO). Commerciallyavailable phosphate esters include PX-200 and PX-202 available fromDaihachi Chemical Iudustry company, and CG-686 and CG-RDP available fromChembridge company.

The phosphazene may be a cyclic phosphazene compound and a linearphosphazene compound. Commercially available phosphazenes includeSPB-100 and SPH-100, both available from Otsuka Chemical company.Examples of the phosphite ester include but are not limited totrimethylphosphite, and triethylphosphite. Examples of the phosphineoxide include but are not limited to tris-(4-methoxyphenyl) phosphineoxide, triphenyl phosphine oxide, diphenyl phosphine oxide, andderivatives thereof. Commercially available phosphine oxides includePQ-60, available from Chin Yee Chemical industry company, and BPO-13 andBPE-3, available from Katayama Chemical Industries company.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of thephosphorus-containing additive flame retardant can range from 0 wt % to25 wt %, and more particularly from 5 wt % to 20 wt %, such as 6 wt %, 7wt %, 8 wt %, 10 wt %, 12 wt %, 13 wt %, 15 wt %, 17 wt %, or 18 wt %.In addition, the amount of the phosphorus-containing additive flameretardant and the phosphorus-containing compound represented by formula(I) are preferably used in an amount such that the total amount of thephosphorus atoms in the resin composition is at least 1 wt %, and morepreferably from 1 wt % to 6 wt %, based on the total weight of the resinsolid content, in order to allow the prepared electronic material tohave good flame retardance, as well as good moisture resistance,dielectric properties and peeling strength, all at the same time.

1.4.3. Phosphorus-Containing Reactive Flame Retardant

The resin composition of the present invention may optionally furthercomprise phosphorus-containing reactive flame retardants to improve theheat resistance and the dimensional stability. As used herein, aphosphorus-containing reactive flame retardant refers to aphosphorus-containing flame retardant having reactive unsaturatedfunctional groups. To meet the halogen-free requirements of the resincomposition of the present invention, the phosphorus-containing reactiveflame retardant is preferably free of halogen. Examples of thephosphorus-containing reactive flame retardant include but are notlimited to an unsaturated functional group-containing phosphoruscompound, such as an allylic cyclic phosphazene compound. Commerciallyavailable phosphorus-containing reactive flame retardant is SPV-100,available from Otsuka Chemical company.

It has been found that compared with the combination of thephosphorus-containing compound (C) represented by formula (I) and thephosphorus-containing additive flame retardant, the combination of thephosphorus-containing compound (C) represented by formula (I) and thephosphorus-containing reactive flame retardant can provide superioroverall properties of the prepared electronic materials, andparticularly provide excellent balance among dimensional stability, heatresistance and peeling strength. In addition, the weight ratio of thephosphorus-containing compound (C) represented by formula (I) to thephosphorus-containing reactive flame retardant is preferably from 4:1 to1:4. When the weight ratio is within the above specified range, theprepared electronic material can have good flame retardance, and canalso have the highest peeling strength and dimensional stability at thesame time.

In the resin composition of the present invention, based on the totalweight of the resin solid content, the amount of thephosphorus-containing reactive flame retardant can range from 0 wt % to50 wt %, and more particularly from 1 wt % to 40 wt %, such as 2 wt %, 3wt %, 4 wt %, 5 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %,13 wt %, 15 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 22 wt %, 23 wt %,24 wt %, 25 wt %, 27 wt %, 28 wt %, 30 wt %, 32 wt %, 33 wt %, 35 wt %,36 wt %, 37 wt %, or 39 wt %. In addition, the amount of thephosphorus-containing reactive flame retardant and thephosphorus-containing compound represented by formula (I) are preferablyused in an amount such that the total amount of the phosphorus atoms inthe resin composition is at least 1 wt %, and more preferably from 1 wt% to 6 wt %, based on the total weight of the resin solid content, toallow the prepared electronic material to have good flame retardance. aswell as good moisture resistance, dielectric properties and peelingstrength, all at the same time.

1.4.4. Filler

The resin composition of the present invention may optionally furthercomprise a filler to improve the mechanical strength, the thermalconductivity and the dimensional stability of the prepared electronicmaterials. Examples of the suitable filler include but are not limitedto silica (for example, spherical silica, fused silica, non-fusedsilica, porous silica, or hollow silica), aluminum oxide, aluminumhydroxide, magnesium oxide, magnesium hydroxide, calcium carbonate,talc, clay, aluminum nitride, boron nitride, silicon nitride, siliconaluminum carbide, silicon carbide, sodium carbonate, magnesiumcarbonate, titanium dioxide, zinc oxide, zirconium oxide, quartz,diamond powder, diamond-like powder, graphite, graphene, potassiumtitanate, strontium titanate, barium titanate, ceramic fiber, zincmolybdate, ammonium molybdate, zinc borate, calcium phosphate, calcinedkaolin, pryan, mica, boehmite, hydrotalcite, carbon nanotube,polytetrafluoroethylene (PTFE) powder, hollow glass bead, nanosizedinorganic powder, and combinations thereof. For providing the low Dk andDf electronic materials that the present invention is particularlytargeted at, it is preferred to use silica or boron nitride.

In the resin composition of the present invention, the shape of thefiller is not particularly limited and may be, for example, a sphericalshape, a fibrous shape, a plate shape, a granular shape, a sheet shape awhiskered shape, or the like, but the present invention is not limitedthereto. In general, the size of the filler is not particularly limited,but to improve the effect of the filler and the quality of the preparedelectronic material, the size of the filler should not be too large. Inthe case of a spherical or granular filler, the average particlediameter is generally less than 10 μm, preferably less than 5 μm, andmore preferably less than 2.5 μm.

In addition, to increase the compatibility between the filler and othercomponents of the resin composition, and the workability of the resincomposition, the filler may be surface-modified with a coupling agentbefore being added into the resin composition. Examples of the couplingagent include but are not limited to a silane coupling agent, a titanatecoupling agent, a zirconate coupling agent, and a poly-siloxane couplingagent. Examples of the silane coupling agent include but are not limitedto epoxy silane, amino silane, vinyl silane, and acrylate silane.Considering the reactivity with a polyphenylene ether resin having anunsaturated functional group, it is preferred to use the vinyl silane asa coupling agent for surface-modification of the filler. Examples of thevinyl silane include but are not limited to vinyltrimethoxy silane andvinyltriethoxy silane. The method for surface-modifying the filler isnot a technical feature of the present invention, and can be easilyaccomplished by persons having ordinary skill in the art based on thedisclosure of the present invention and the ordinary skill. Detaileddescription for the surface-modification method of the filler can bealso found in, for example, U.S. patent application Ser. No. 6,524,717B1, the subject matter of which is incorporated herein in its entiretyby reference.

Commercially available fillers include the Admafuse series, the Admafineseries, and the Admanano series of silica products, and SC1050, SC2050,SC4050, SC5500, and SE2050, available from Admatechs company.

In the resin composition of the present invention, based on the totalweight of the resin composition, the amount of the filler can range from0 wt % to 40 wt %, and more particularly from 5 wt % to 35 wt %, such as7 wt %, 8 wt %, 10 wt %, 12 wt %, 13 wt %, 15 wt %, 17 wt %, 18 wt %, 20wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28wt %, 29 wt %, 30 wt %, 32 wt %, or 34 wt %.

1.4.5. Polymerization Initiator

The resin composition of the present invention may optionally furthercomprise polymerization initiators to assist with inducingpolymerization. Examples of the polymerization initiators include butare not limited to azobisisobutyronitrile,azobis(2-isopropyl)butyronitrile, azobisisoheptonitrile, dibenzoylperoxide, acetylisobutyryl peroxide, diacetyl peroxide,2,4-dichlorobenzoyl peroxide, 2-dimethylbenzoyl peroxide, lauroylperoxide, diisopropyl peroxydicarbonate, bis(3,5,5 -trimethylhexanoyl)peroxide, cyclohexanone peroxide, methyl ethyl ketone peroxide,dicyclohexylpropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate,bis(4-tert-butylcyclohexyl) peroxydicarbonate, bis(2-ethylhexyl)peroxydicarbonate, bis(2-phenylethoxy) peroxydicarbonate, dihexadecylperoxydicarbonate, tert-butyl peroxybenzoate, tert-butylperoxyphenylacetate, peracetic acid, tert-butyl peroxypivalate,tert-hexyl peroxypivalate, cumyl peroxyneodecanoate, tert-butylhydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, dicumylperoxide, ditert-butyl peroxide, hydrogen peroxide, ammonium persulfate,potassium persulfate, peroxide-alkyl metal, and oxy-alkyl metal.

Commercially available polymerization initiator include PERBUTYL P,PERHEXA 25B, and PERHEXYNE 25B, both available from Nippon Oil & Fats(NOF) company. In the resin composition of the present invention, basedon the total weight of the resin solid content, the amount of thepolymerization initiator can range from 0 wt % to 3 wt %, and moreparticularly from 0.05 wt % to 2.5 wt %, such as 0.07 wt %, 0.08 wt %,0.09 wt %, 1.0 wt %, 1.1 wt %, 1.2 wt %, 1.3 wt %, 1.4 wt %, 1.5 wt %,1.6 wt %, 1.7 wt %, 1.8 wt %, 1.9 wt %, 2.0 wt %, 2.1 wt %, 2.2 wt %,2.3 wt %, or 2.4 wt %.

1.4.6. Epoxy Resin

The resin composition of the present invention may optionally furthercomprise an epoxy resin to improve the physicochemical properties of theprepared electronic material. As used herein, an epoxy resin refers to athermal hardening resin with at least two epoxy functional groups ineach molecule, including but being not limited to a bifunctional epoxyresin, a tetrafunctional epoxy resin, an octafunctional epoxy resin, ora linear phenolic epoxy resin. In the resin composition of the presentinvention, the type of the epoxy resin is not particularly limited. Theepoxy resin can be used by persons having ordinary skill in the artdepending on the need based on the disclosure of the present invention.However, in order to meet the halogen-free requirements of the resincomposition of the present invention, the epoxy resin should be ahalogen-free epoxy resin, and particularly a bromine-free epoxy resin.

To avoid adverse effects on the dielectric properties and heatresistance of the prepared electronic material, it is preferred to usean epoxy resin having a high glass transition temperature (Tg), low Dkand low Df. For example, a dicyclopentadiene (DCPD)-typed epoxy resinmay be used.

1.4.7. Curing Agent and Curing Accelerator

In the case that the resin composition comprises an epoxy resin, acuring agent and a curing accelerator may be further added to promotethe ring-opening reaction of epoxy functional groups and lower thecuring reaction temperature. The type of the curing agent is notparticularly limited as long as it can promote the ring-opening reactionof epoxy functional groups and lower the curing reaction temperature.The curing agent is suitably selected from but are not limited to an OHgroup-containing compound, an amine-containing compound, an acidanhydride compound, and an active ester compound, wherein each mentionedcuring agent can either be used alone or in combination. Examples of thecuring agent include but are not limited to phenolic resin, styrenemaleic anhydride (SMA), dicyandiamide, diaminophenylsulfone,dianilinomethane, phenolic resin, aromatic diamine, aromaticdianhydride, aliphatic dianhydride, benzoxazine resin, cyanate resin,phenolic triazine resin, and copolymer of styrene and vinylphenol. Ingeneral, based on the total weight of the resin solid content, theamount of the curing agent can range from 5 wt % to 25 wt %, but thepresent invention is not limited thereto. Persons with ordinary skill inthe art can adjust the amount of the curing agent depending on the need.

The curing accelerator is suitably selected from but are not limited toa tertiary amine, a quaternary ammonium salt, a imidazole, or apyridine, wherein each mentioned curing accelerator can either be usedalone or in combination. Examples of the pyridine include but are notlimited to 2,3-diaminopyridine, 2,5-diaminopyridine,2,6-diaminopyridine, 4-dimethylaminopyridine, 2-amino-3-methylpyridine,2-amino-4-methylpyridine, or 2-amino-3-nitropyridine. In general, basedon the total weight of the resin solid content, the amount of the curingaccelerator can range from 0.55 wt % to 5 wt %, but the presentinvention is not limited thereto. Persons with ordinary skill in the artcan adjust the amount of the curing accelerator depending on the need.

1.5. Preparation of Resin Composition

The resin composition of the present invention may be prepared into avarnish for subsequent applications by evenly mixing the polyphenyleneether resin, the cross-linking agent, the phosphorus-containing compoundrepresented by formula (I) and other optional components through astirrer, and dissolving or dispersing the obtained mixture into asolvent. The solvent here can be any inert solvent that can dissolve ordisperse the components of the resin composition of the presentinvention but does not react with the components of the resincomposition. Examples of the solvent that can dissolve or disperse thecomponents of the resin composition include but are not limited totoluene, γ-butyrolactone, methyl ethyl ketone, cyclohexanone, butanone,acetone, xylene, methyl isobutyl ketone, N,N-dimethylformamide (DMF),N,N-dimethylacetamide (DMAc), and N-methylpyrolidone (NMP), wherein eachmentioned solvent can either be used alone or in combination. The amountof the solvent is not particularly limited as long as the components ofthe resin composition can be evenly dissolved or dispersed therein. Insome embodiments of the present invention, a mixture of toluene, methylethyl ketone and γ-butyrolactone is used as the solvent.

2. PREPREG

The present invention also provides a prepreg prepared from theabovementioned resin composition, wherein the prepreg is prepared byimpregnating a substrate with the abovementioned resin composition or bycoating the abovementioned resin composition onto a substrate and dryingthe impregnated or coated substrate. The method for preparing theprepreg is not particularly limited, and can be easily accomplished bypersons having ordinary skill in the art based on the disclosure of thepresent invention and the ordinary skill. Specifically, the method forimpregnating or coating resin compositions include but are limited toimpregnating, roll coating, die coating, bar coating, and spraying. Theimpregnated or coated substrate can be dried at a temperature of 80° C.to 180° C. for 1 to 10 minutes to obtain a semi-cured (B-stage) prepreg.

The ordinary substrates comprise glass fiber reinforcing materials(e.g., glass-fiber woven fabrics, glass papers, glass mats, etc.), kraftpapers, short fiber cotton papers, nature fiber cloths, and organicfiber cloths. Examples of the substrate include but are not limited towoven fabrics, non-woven fabrics, glass roving cloths, glass cloths,chopped glass fibers, hollow glass fibers, glass mats, glass surfacingmats, non-woven glass fabrics, and ceramic fiber fabrics. Examples ofthe raw material that can be used to form the substrate include but arenot limited to E-glass fiber, NE-glass fiber, S-glass fiber, L-glassfiber, T-glass fiber, D-glass fiber, quartz, aramid, and liquid crystalpolymer. Considering the dielectric properties of the preparedelectronic material, it is preferred to use a substrate having a low Dfvalue, such as a substrate composed of E-glass fiber, NE-glass fiber,S-glass fiber, and L-glass fiber.

In some embodiments of the present invention, a 2116 glass fiber clothis used as the substrate. The substrate is heated and dried at 175° C.for 2 to 15 minutes (B-stage) to provide a semi-cured prepreg.

3. METAL-CLAD LAMINATE AND PRINTED CIRCUIT BOARD

The present invention also provides a metal-clad laminate prepared fromthe abovementioned prepreg, which comprises a dielectric layer and ametal layer. The metal-clad laminate can be prepared by laminating theabovementioned prepreg and a metal foil, or by coating the resincomposition onto a metal foil and then drying the coated metal foil,wherein the dielectric layer is provided by the abovementioned prepreg.In the case of the preparation of the metal-clad laminate by using theprepreg, the metal-clad laminate can be prepared by superimposing aplurality of the abovementioned prepregs, superimposing a metal foil(such as a copper foil) on at least one external surface of thedielectric layer composed of the superimposed prepregs to provide asuperimposed object, and then performing a hot-pressing operation ontothe superimposed object to obtain the metal-clad laminate.

Furthermore, the abovementioned metal-clad laminate can form a printedcircuit board by further patterning the external metal foil thereof.

4. EXAMPLES

4.1. Testing Method

The present invention is further illustrated by the embodimentshereinafter, wherein the testing instruments and methods are as follows:

[Dielectric constant (Dk) and dissipation factor (Df) measurement]

The dielectric constant (Dk) and dissipation factor (Df) of themetal-clad laminate are measured according to IPC-TM-650 2.5.5.13 underan operating frequency of 10 GHz. The resin content (RC) of the testedprepreg in the metal-clad laminate is about 54%.

[Flame Retardance Test]

The flame retardance test is carried out according to UL94V (VerticalBurn), which comprises the burning of a laminate, which is heldvertically, using a Bunsen burner to compare its self-extinguishingproperties and combustion-supporting properties. The ranking for theflame retardance level is V0>V1>V2.

[Dimensional Stability Test]

A sample to be tested is prepared by laminating four prepregs. Accordingto IPC-TM-650 2.4.24.5, the dimensional stability test is carried out byusing a thermal mechanical analyzer (TMA) to measure the coefficient ofthermal expansion (CTE) α1 and the rate of change of the coefficient ofthermal expansion in the Z-axis direction (total z-CTE) of the sample tobe tested at temperatures below Tg thereof. The α1 is measured in atemperature range from 50° C. to 120° C., and the unit thereof is ppm/°C. The total z-CTE is measured in the temperature range from 50° C. to260° C., and the unit thereof is %.

[Peeling Strength Test]

The peeling strength refers to the bonding strength between the metalfoil and hot-pressed laminated prepreg and is expressed as the forcerequired to vertically peel clad copper foil with a width of ⅛ inch fromthe surface of the hot-pressed laminated prepreg. The unit of thepeeling strength is pounds per inch (lbf/in).

[Heat Resistance Test]

A heat resistance test is carried out by immersing the dried metal-cladlaminate in a solder bath at 288° C. for 100 seconds, repeating theabovementioned immersion three times, and subsequently measuring thepeeling strength for heat resistance of the metal-clad laminate. Then,the decrease in the peeling strength for the heat resistance of themetal-clad laminate is calculated by comparing it to that of ametal-clad laminate that has not been immersed in the solder bath(hereinafter called “original peeling strength”). If the decrease in thepeeling strength for heat resistance is 5% or less of the originalpeeling strength, it indicates that the heat resistance is excellent,and the test result is recorded as “∘”; if the decrease in the peelingstrength for heat resistance is 6% to 15% of the original peelingstrength, it indicates that the heat resistance is normal, and the testresult is recorded as “Δ”; and if the decrease in the peeling strengthfor heat resistance is 16% or more of the original peeling strength, itindicates that the heat resistance is not good, and the test result isrecorded as “X”.

4.2. Raw Materials Used in Examples and Comparative Examples List:

TABLE 1 Raw Materials List Model No. Description OPE-2st Polyphenyleneether resin having an unsaturated functional group, available fromMitsubishi Gas Chemical Company SA9000 Polyphenylene ether resin havingan unsaturated functional group, available from Saudi Basic IndustryCorporation (SABIC) TAIC Cross-linking agent, triallyl isocyanurate,available from Evonik Company BMI 5100 Cross-linking agent,bismaleimide, available from Daiwa Fine Chemical Company BP-PZPhosphorus-containing compound represented by formula (I), availablefrom Otsuka Chemical Company, phosphorus content: 13% Ricon 150Vinyl-containing elastomer, available from Cray Valley Company SPB-100Phosphorus-containing additive flame retardant, available from OtsukaChemical Company, phosphorus content: 13% PX-200 Phosphorus-containingadditive flame retardant, available from Daihachi Chemical IudustryCompany, phosphorus content: 9% SPV-100 Phosphorus-containing reactiveflame retardant, available from Otsuka Chemical Company, phosphoruscontent: 13% SC-5500 SVJ Silica filler surface-modified with vinylsilane, available from Admatechs Company, average particle diameterbeing 1.51 μm Perbutyl P Polymerization initiator, available from NipponOil & Fats Company

4.3. Preparation of Resin Composition

The resin compositions of Examples 1 to 16 and Comparative Examples 1 to5 were prepared according to the constitutions shown in Tables 2-1 to2-3, and 3, wherein each of the components was mixed at room temperaturewith a stirrer, and toluene, methyl ethyl ketone and γ-butyrolactone,all available from Fluka company, as a solvent were added thereinto,followed by stirring of the resultant mixture at room temperature for 60to 120 minutes, which each of the resin compositions was obtained. Thetotal amount of the phosphorus atoms was calculated based on the resinsolid content.

TABLE 2-1 Constitutions of the resin compositions of Examples 1 to 6Examples Unit: Parts by weight 1 2 3 4 5 6 Polyphenylene ether OPE-2st50 50 50 50 50 50 resin Cross-linking agent BMI 5100 20 20 20 20 20 20Elastomer Ricon 150 30 30 30 30 30 30 Phosphorus-containing BP-PZ 30 2525 10 25 10 compound of formula (I) Phosphorus-containing SPB-100 10 25additive flame PX-200 10 retardant Phosphorus-containing SPV-100 10 25reactive flame retardant Filler SC-5500 SVJ 45 45 45 45 45 45Polymerization Perbutyl P 2 2 2 2 2 2 initiator Phosphorus-containingadditive 100:0 100:0 100:0 100:0 71:29 29:71compound:phosphorus-containing reactive compound (weight ratio) Totalamount of phosphorus atoms 3.0 3.3 3.0 3.3 3.3 3.3 (wt %)

TABLE 2-2 Constitutions of the resin compositions of Examples 7 to 12Examples Unit: Parts by weight 7 8 9 10 11 12 Polyphenylene ether SA900035 35 35 35 35 35 resin OPE-2st 30 30 30 30 30 30 Cross-linking agentTAIC 35 35 35 35 35 35 Phosphorus-containing BP-PZ 30 15 75 25 25 20compound of formula (I) Phosphorus-containing SPB-100 10 additive flameretardant Phosphorus-containing SPV-100 10 15 reactive flame retardantFiller SC-5500 SVJ 45 45 45 45 45 45 Polymerization Perbutyl P 2 2 2 2 22 initiator Phosphorus-containing additive 100:0 100:0 100:0 100:0 71:2957:43 compound:phosphorus-containing reactive compound (weight ratio)Total amount of phosphorus atoms 3.0 1.7 5.5 3.3 3.4 3.3 (wt %)

TABLE 2-3 Constitutions of the resin compositions of Examples 13 to 16Unit: Examples Parts by weight 13 14 15 16 Polyphenylene ether SA9000 3535 35 35 resin OPE-2st 30 30 30 30 Cross-linking agent TAIC 35 35 35 35Phosphorus-containing BP-PZ 25 10 3 9 compound of formula (I)Phosphorus-containing SPV-100 5 12 12 35 reactive flame retardant FillerSC-5500 SVJ 45 45 45 45 Polymerization Perbutyl P 2 2 2 2 initiatorPhosphorus-containing additive 83:17 45:55 20:80 20:80 compound:phosphorus-containing reactive compound (weight ratio) Total amount ofphosphorus atoms 3.0 2.3 1.7 4.0 (wt %)

TABLE 3 Constitutions of the resin compositions of Comparative ExamplesComparative Examples Unit: Parts by weight 1 2 3 4 5 Polyphenylene etherSA9000 50 50 50 50 50 resin Cross-linking agent BMI 5100 20 20 20 20 20Elastomer Ricon 150 30 30 30 30 30 Phosphorus-containing SPB-100 30 25additive flame PX-200 20 retardant Phosphorus-containing SPV-100 10 1535 reactive flame retardant Filler SC-5500 SVJ 45 45 45 45 45Polymerization Perbutyl P 2 2 2 2 2 initiator Phosphorus-containingadditive 100:0 71:29 57:43 0:100 compound:phosphorus-containing reactivecompound (weight ratio) Total amount of phosphorus atoms 3.0 3.3 2.7 3.3(wt %)

4.4. Preparation and Properties of Metal-Clad Laminate

The metal-clad laminates of Examples 1 to 16 and Comparative Examples 1to 5 were respectively prepared by using the prepared resincompositions. In detail, one of the resin compositions of Examples 1 to16 and Comparative Examples 1 to 5 was coated on glass fiber cloths(type: 2116; thickness: 0.08 mm) by a roller at a controlled thickness.The coated glass fiber cloths were then placed in an oven and dried at175° C. for 2 to 15 minutes to produce prepregs in a half-cured state(B-stage) (the resin content of the prepreg was about 54%). Four piecesof the prepregs were superimposed and two sheets of copper foil (0.5oz.) were respectively superimposed on both of the two external surfacesof the superimposed prepregs to provide a superimposed object. Ahot-pressing operation was performed on each of the prepared objects.The hot-pressing conditions were as follows: heating to about 200° C. to220° C. at a heating rate of 3.0° C./min, and hot-pressing for 180minutes under a full pressure of 15 kg/cm² (initial pressure is 8kg/cm²) at said temperature.

The properties of the prepregs and metal-clad laminates of Examples 1 to16 and Comparative Examples 1 to 5, including flame retardance, peelingstrength, dielectric constant (Dk), dissipation factor (Df), coefficientof thermal expansion α1, rate of change of coefficient of thermalexpansion in the Z-axis direction (total z-CTE), and heat resistancetest were measured according to the aforementioned testing methods, andthe results are tabulated in Tables 4 and 5.

TABLE 4 Properties of the prepregs and the metal-clad laminates ofExamples Flame Heat retard- Total Peeling resis- Dk Df ance α1 z-CTEstrength tance Unit ppm/ ° C. % lbf/in Exam- 1 3.8 0.0043 V1 42 2.0 3.3∘ ples 2 3.8 0.0045 V0 46 2.8 3.7 Δ 3 3.8 0.0045 V0 41 2.7 3.6 Δ 4 3.80.005 V0 47 2.9 3.8 Δ 5 3.8 0.0046 V0 34 2.1 4.1 ∘ 6 3.8 0.0047 V0 382.3 4.5 ∘ 7 3.9 0.0041 V1 39 1.9 3.4 ∘ 8 3.9 0.0042 V1 41 2.2 3.5 ∘ 93.9 0.0040 V0 38 1.9 3.2 Δ 10 3.9 0.0045 V0 43 2.6 3.8 Δ 11 3.9 0.0046V0 35 2.0 4.3 ∘ 12 3.9 0.0046 V0 36 2.0 4.3 ∘ 13 3.9 0.0042 V0 34 2.04.0 ∘ 14 3.9 0.0046 V0 37 2.5 4.3 ∘ 15 3.9 0.0047 V0 38 2.6 4.7 ∘ 16 3.90.0048 V0 37 3.0 4.5 ∘

TABLE 5 Properties of the prepregs and the metal- clad laminates ofComparative Examples Flame Heat retard- Total Peeling resis- Dk Df anceα1 z-CTE strength tance Unit ppm/ ° C. % lbf/in Compar- 1 3.8 0.004Burning 48 2.2 4.0 ∘ ative 2 3.8 0.005 V2 75 4.3 4.1 x Exam- 3 3.8 0.005V1 60 3.8 3.8 Δ ples 4 3.8 0.005 V1 56 3.6 3.6 Δ 5 3.9 0.005 V1 51 3.54.3 ∘

As shown in Table 4, each of the electronic materials prepared from thehalogen-free low dielectric resin composition of the present inventionexhibits satisfactory physicochemical properties and dielectricproperties (e.g. peeling strength, flame retardance, Dk, Df, heatresistance, and so on), and possesses excellent dimensional stability(α1 and total z-CTE are low). Furthermore, as shown in Examples 2 to 6and 10 to 16, when the resin composition of the present inventionfurther comprises a phosphorus-containing additive flame retardant or aphosphorus-containing reactive flame retardant, the flame retardance andthe peeling strength of the prepared electronic material can be furtherimproved. In particular, as shown in Examples 5, 6 and 11 to 16, whenthe resin composition of the present invention further comprises thephosphorus-containing reactive flame retardant, not only can the flameretardance and peeling strength of the prepared electronic materials befurther improved, but also, the dimensional stability thereof can besignificantly improved.

In contrast, as shown in Table 5, electronic materials prepared by usingresin compositions other than that of the present invention cannotachieve a satisfactory level in all physicochemical properties anddielectric properties, and do not have good dimensional stability.Specifically, as shown in Comparative Example 1, when the resincomposition does not comprise the phosphorus-containing compoundrepresented by formula (I) and any phosphorus-containing flameretardant, the prepared electronic material does not exhibit flameretardance. As shown in Comparative Example 2, when the resincomposition does not comprise the phosphorus-containing compoundrepresented by formula (I) but does comprise the phosphorus-containingadditive flame retardant, the flame retardance, heat resistance anddimensional stability of the prepared electronic material are poor. Inaddition, as shown in Comparative Examples 3 to 5, when the resincompositions do not comprise the phosphorus-containing compoundrepresented by formula (I) but do comprise a phosphorus-containingreactive flame retardant or a combination of a phosphorus-containingadditive flame retardant and a phosphorus-containing reactive flameretardant, the prepared electronic materials exhibit acceptable flameretardance, but still do not have satisfactory dimensional stability.

The above examples are used to illustrate the principle and efficacy ofthe present invention and show the inventive features thereof. Peopleskilled in this field may proceed with a variety of modifications andreplacements based on the disclosures and suggestions of the inventionas described without departing from the principle and spirit thereof.Therefore, the scope of protection of the present invention is that asdefined in the claims as appended.

What is claimed is:
 1. A halogen-free low dielectric resin composition,comprising: (A) a polyphenylene ether resin having an unsaturatedfunctional group; (B) a cross-linking agent having an unsaturatedfunctional group; and (C) a phosphorus-containing compound representedby the following formula (I):


2. The halogen-free low dielectric resin composition of claim 1, furthercomprising a reactive phosphorus compound having an unsaturatedfunctional group.
 3. The halogen-free low dielectric resin compositionof claim 2, wherein the weight ratio of the phosphorus-containingcompound (C) represented by formula (I) to the reactive phosphoruscompound is from 4:1 to 1:4.
 4. The halogen-free low dielectric resincomposition of claim 2, wherein the reative phosphorus compound is anallyl cyclophosphazene compound.
 5. The halogen-free low dielectricresin composition of claim 1, wherein the polyphenylene ether resin (A)is represented by the following formula (II):

wherein, R₃₁, R₃₂, R₃₃ and R₃₄ are independently H, or a substituted orunsubstituted C1-C5 alkyl; A₁ and A₂ are independently

X and Y are independently absent, or carbonyl or an alkenyl-containinggroup; m and n are independently an integer from 0 to 100, with theproviso that m and n are not 0 at the same time; and Z is absent, oraryl, —O—,

wherein R₃₅ and R₃₆ are independently H or a C1-C12 alkyl.
 6. Thehalogen-free low dielectric resin composition of claim 1, wherein thecross-linking agent (B) is selected from the group consisting of apolyfunctional allylic compound, a polyfunctional acrylate, apolyfunctional acrylamide, a polyfunctional styrenic compound, abismaleimide compound, and combinations thereof.
 7. The halogen-free lowdielectric resin composition of claim 1, wherein the cross-linking agent(B) is selected from the group consisting of triallyl isocyanurate(TAIC), triallyl cyanurate (TAC), prepolymers thereof, and combinationsthereof.
 8. The halogen-free low dielectric resin composition of claim1, further comprising a phosphorus-containing additive flame retardantselected from the group consisting of a phosphinate salt, apolyphosphate salt, a phosphonium salt, a phosphate ester, aphosphazene, a phosphite ester, a phosphine oxide, and combinationsthereof.
 9. The halogen-free low dielectric resin composition of claim1, further comprising a vinyl-containing elastomer.
 10. The halogen-freelow dielectric resin composition of claim 9, wherein thevinyl-containing elastomer is selected from the group consisting ofpolybutadiene, styrene-butadiene (SB) copolymer,styrene-butadiene-styrene (SBS) di/tri-block copolymer, polyisoprene,styrene-isoprene copolymer, styrene-isoprene-styrene (SIS) blockcopolymer, acrylonitrile-butadiene copolymer,acrylonitrile-butadiene-styrene block copolymer, and combinationsthereof.
 11. The halogen-free low dielectric resin composition of claim9, wherein the cross-linking agent (B) is a bismaleimide compound. 12.The halogen-free low dielectric resin composition of claim 1, furthercomprising a filler selected from the group consisting of silica,aluminum oxide, aluminum hydroxide, magnesium oxide, magnesiumhydroxide, calcium carbonate, talc, clay, aluminum nitride, boronnitride, silicon nitride, silicon aluminum carbide, silicon carbide,sodium carbonate, magnesium carbonate, titanium dioxide, zinc oxide,zirconium oxide, quartz, diamond powder, diamond-like powder, graphite,graphene, potassium titanate, strontium titanate, barium titanate,ceramic fiber, zinc molybdate, ammonium molybdate, zinc borate, calciumphosphate, calcined kaolin, pryan, mica, boehmite, hydrotalcite, carbonnanotube, polytetrafluoroethylene (PTFE) powder, hollow glass bead,nanosized inorganic powder, and combinations thereof.
 13. Thehalogen-free low dielectric resin composition of claim 1, wherein, basedon the total weight of the resin solid content, the amount of thephosphorus-containing compound (C) represented by formula (I) is 1 wt %to 50 wt %.
 14. The halogen-free low dielectric resin composition ofclaim 1, wherein the weight ratio of the polyphenylene ether resin (A)to the cross-linking agent (B) is from 3:1 to 1:1.
 15. A prepreg, whichis prepared by impregnating a substrate with the halogen-free lowdielectric resin composition of claim 1 or by coating the halogen-freelow dielectric resin composition of claim 1 onto a substrate and dryingthe impregnated or coated substrate.
 16. A metal-clad laminate, which isprepared by laminating the prepreg of claim 15 and a metal foil.
 17. Aprinted circuit board, which is prepared from the metal-clad laminate ofclaim
 16. 18. A metal-clad laminate, which is prepared by coating thehalogen-free low dielectric resin omposition of claim 1 onto a metalfoil and drying the coated metal foil.
 19. A printed circuit board,which is prepared from the metal-clad laminate of claim 18.